A cool glass of water sits before me looking very inviting. As I reach out for the glass I ponder (that’s right! not for me this regular thinking business; pondering is what I do.)

It is sometime in the late 18^th century. In a room somewhere in Germany a man stands with a flask in his hand. He places an ingredient into the flask and fills the flask with water. He is trying to be precise: he wants the flask to contain one part ingredient to a hundred parts water. The man is Samuel Hahnemann. He has invented homeopathy. He has has just made a 1C homeopathic solution.

Samuel Hahnemann takes some of his 1C solution and dilutes it, again using one part solution to one hundred parts water. He now has a 2C solution. He repeats the process (3C) and again (4C) until he reaches his goal, a 15 C solution. He has now diluted his original ingredient 10³⁰ times (for those that can’t remember mathematical notations, 10³⁰ is a one followed by thirty zeroes.)

“Mr. Hahnemann?”

“Ah, Mr. Jones. You have a question?”

“Indeed, I do. Do you realize that you have, at best, only one or two molecules of your original ingredient in that flask? In fact, it most likely has no molecules of the ingredient?”

“Of course it has molecules.”

“Maybe one or two at best. Let’s take a closer look at your process. Suppose you were using 56 grams of iron as your ingredient. Those 56 grams contain 6.02×10²³ (Avogadro’s number) molecules. After your 1C dilution you are left with about 10²² molecules. After 2C, 10²⁰ molecules. After 10C you are left with 10,000 molecules. By the time you reach 12C you have, at best, one or two, but most likely no molecules left.”

“Hmmmm!”

It is sometime in the late 20^th century. Homeopaths now recognize that very little, if any, of the original ingredient remains after several dilutions. The curative powers of nothing seem silly even to them so they have come up with a new mechanism for homeopathy. It isn’t necessary, they say, that any of the ingredient’s molecules remain at all. They have “discovered” that water has “memory” and remembers the ingredient.

“Mr. Homeopath?”

“Ah, Mr. Jones. You have a question?”

“This water memory, it seems to be extremely selective, doesn’t it?”

“How so?”

“It seems like water only remembers the ingredient that you, the homeopath, want it to remember and completely forgets about every other type of molecule it met in the past. It can’t recall the molecules of bottles, tanks, fish poop. Nothing but the ingredient.”

“Well, we do use the purest water.”

“One with no other molecules in it?”

“That’s right. No other… um…”

And so I finished pondering and drank my glass of water. The water came out of the faucet in the kitchen so it should have met many a molecule along its way. I wonder which one it remembered. Probably something arid because it cured me of thirst.

Dr. Stephen Barrett has an excellent review of homeopathy on Quackwatch. The Reader Responses are worth looking at.

Several other sceptical blogs deal with homeopathy. JREF is a good place to start while Thinking Is Real has a nice post on homeopathy and the “swine” flu.

EDITED: changed from hydrogen molecules to iron since water molecules have a couple of hydrogen atoms happily bonding with an oxygen atom.